Modern telecommunication systems utilize a number of materials and mediums to transmit information. Recently, cables, such as fiber optic cables, have become more popular in the communication industry and have begun to replace electrical wires. Fiber optic cables include transparent optical fibers made of glass or plastic and are capable of transmitting voice, video, and data. Compared to electrical wires, fiber optic cables permit signals to travel longer distances with less loss and less electromagnetic interference.
One type of fiber optic cable used to transmit data across aerial transmission lines is all-dielectric self-supporting (ADSS) cables. Such cables typically have a strong non-metallic sheath that supports the optical fibers making up the cable. An ADSS cable may also have a reinforcing strand at its core. All-dielectric cable has the advantage that it can be used in close proximity to electrical power lines, whereas conventional communication cables are required to be run in a separate zone, usually at least forty inches below the power cables and above ground neutral. Other types of fiber optic cable lines include, encased with ground wire, encased within phase conductor, and wrapped around phase conductor or ground wire cables.
Fiber optic cable is typically installed on aerial transmission routes in long lengths so as to minimize the number of splices, each of which degrades optical signals and is expensive. Because of certain problems related with splicing, such as expense and the induced increase in noise, it is generally more desirable to overbuild the amount of cable used and store the excess cable, as opposed to splicing and adding cable in the future. To allow for rerouting, due to pole movement and for repairs, slack is provided in the form of surplus lengths of cable at intervals along the route.
While fiber optic drop wire is similar to fiber optic cable, drop wire has some distinctive characteristics. Like fiber optical cable, fiber optic drop wire must be provided with means for supporting a surplus length of drop wire and protecting it against over-bending. In the case of fiber optic cable, any surplus length of cable is contiguous with the main run. However, in the case of fiber optic drop wire, a surplus length of drop wire must be provided in conjunction with a separate independent run that is directed away from the main run of cable in order to terminate at the subscriber location. The fiber optic drop wire originates from a closure connected to the main cable run where, most often, multiple drop wires also originate to be routed to various different subscriber locations.
Storing surplus cable poses problems as optical cable has a minimum bend radius and is vulnerable to damage (fiber breakage) from bending and twisting, if the minimum radius is exceeded.